Method and apparatus for swaging internal threads



May 6, 1958 A. J. RICHARDS 2,832,972

METHOD AND APPARATUS FOR SWAYING INTERNAL THREADS Filed Feb. 16, 1953 nited 1 METHOD AND APPARATUS FOR SWAGING q 'INTERNALTimEADS- The present invention relates 'to a screw threaded fastening device, and has foran. object to provide a fasted ing device having ascrew thread formed in a metal blank by a pressing operation with a shaped punch. it is a further object of the present invention to provide a fastening device having a screwthread formed in the aperture of a metal blank by metal displaced from adjacent its'end. 1 V w It is: still arfurther object of the present invention to provide rac'fa'steningtdevice that can she fabricatedin a continuous operation from a stripof metal;

t is another object of the present invention to provide a fastening device thatis economical totmanufacture and can he made in. various shapes in the pressing .operation. --Other objects=and features ofstheinvention will become apparent as-the description proceedsespecially: when taken in conjunction with the accompanying drawings wherein 1.

Figure l is a view of one face of the device.

Figure 2 isla sectional .viewv taken through. line 2-2, Fig. 1. I. j

Figure 3 is a view of the opposite face of the device showninFigl.

Figure t is. a sectional view taken through line 4-4, Fig,3, y.

Figure 5 is a sectional view of the blank before the thread-is pressed inplace.

Figure 6-.. is a side elevation of the punch used to press the threadin the-blank. 5. c.

Figure 7 is a plan view of the punch looking in the directionof thearrows 7-7 in Eig. 6. 1;.

Figure 8= is.-a2side"elevationpartly in section showing the blank on the locating pinand thetpunch inposition afterpressing'in a thread.

Figure 9 is a side'elevation of the pin used for locating the blank .after the portion of. theithread hassbeen pressed'in from one side. n :I 1

' Fig. 10 is a plan view looking in the direction of the arrowsih-itlyFigQ; .l. j

Figure llxis a side elevation partly in section showing the blank on the'locating. pin and thepunch imposition after pressing in a portion of the thread fro-m the face opposite to that in which. a thread hasalready beenpressed.

Figure-l2 shows a modified form of the invention partly in section. Y

Referring to the drawings the blank 10 preferably of soft" steel has an aperture 11 extending .therethrough. The aperture is roundand can be punched out of the metal by means'of a punch andv die. The diameter of the'aperture is determined from :the size of the thread to be pressed and is approximately equal ot the major diameter of the thread formed.

tioned infa :die block 22 so that its axis is directly in line tes Pater";

' aperture;

ice

with the axis of the pin 12. It will be understood that the die, blocks indicated at 14 and 22 can be used with any conventional die sets. or type of apparatus suitable for the purpose of performing a pressing operation. I v.The punch Ztlis made, from a tool steel thatcan be suitably. hardened and,has a spiral shapedsurface. Sit that is axially and radially perpendicularto the axis of the punch. The radius of the inner edge 32 of the surface 30 is concentric with the axis of the punch and is equal to one half of the major diameter of thethread formed by the punch; The edge 32 has a-helix angle approximately equal to the helix angle, when taken on the major diameter, of the thread formed by the punch. The thread shaping surface 34 extends from edge 32 towards the axis of the pu n ch at an angle -of 30. degree s with the surface 30. V The inner edge 35 of the surface 34 has, a radius, equal to one halfof the minor diameter of the threadi'ormed-hy the punch and-has a helix angle approximately, equal .to the helix angle, when taken on the minordiameter, oi-the thread formed by the punch. The metal deforming surface 36 is-substantially axially and radially;perpendiculartothe; axis of the .punch; flhe outer edge 38 of thesurface St} is eccentric with the axis of the punch beginning. at point 41) having the smallest radius and gradually increasing in radius to the point The edge; 38 isrsharp enabling it. toshear the metal of the blank. The edge 4-2 has the same radius astheradius of the aperture 11 of the blank. I

As the punch ismoved toward the blank thepoint 40 makes initial. contact and as the punch is, forced, into the blank the edge 38 shears the metal progressively along its lengthtforcing the metal inwardly against-,thesurface 34 and downwardlydnto the aperturetoform afportion of the'thread. The point 49. moves further, downward intothe metal than the point 41.,and therefore less. radial thickness of metal off of the wallof the aperture is required. .to be forced. inwardly and downwardly. at the point 40. than is requiredatpoint 41 to formta thread of equal fullness around the periphery of the aperture. The. punchisforcedinto the metal until the pointtdd is into the aperture adistance of one half of the thickness of..the..blank. The area. of the surface-Siddeteruiines the amount. of metal forced into the, apertureio: form the thread. This'a'rea is developedaccording tothe size and pitch of the thread to be. formed. and thethickness of the blank to housed. and is of..a size to provide. a thread of-equal fullness around the periphery .of the A blank of sufficient thicknessfis .used so that the punch :will penetratelfar enough. into themetallto allow the edge 38 toiform. a shoulder 45 in the blank for purposes later to bendescribed. vWhen the proper amount ofmetal has been displaced it has'been found that theside 46 of thethread. willassum'e a forin thatwill give a symmetrical thread having approximately a 60 degree angle. After forming this portion of the thread the punch is withdrawn from the blank. l i

The amount of metal displaced by the punch also varies with theangle the spiral surface makes with the axis of the punch. Figure 12 shows a modification oftheinvention in which the punch 47 is the same'as punch 20 previously described with the exception that the spiral surface 48 instead of being axially and radially perpendicular or 9 0 degrees with the axis of the punch is axially and radially angular or less than degrees with the axis of the punch. By varying this angle the fullness of the thread formed will vary. I g V Figure 12 also shows a modification of the locating pin used in forming the thread. The pin 49 is similar to pin 12 previously described and has an upstandingjpor'tion 50 of a diameter to fit snugly into the aperture li of the blank. The surface 51 is made to-conform to meanderside of the thread that is to be formed by the punch used with the pin. Either the punch 20 or the modified punch 47 can be used with the pin. The punch is pressed into the blank-forcing the metal downwardly and inw ardly against the surface 51. The portion 50 is made of a length to project into the aperture a distance required to position the thread where desired in the aperture and where a full thread will be obtained when the punch is stopped just short of contact with the pin. A thread of 7 the same contour as the edge and the edge portion 56 has the same radius as the edge 42 of the punch 20. The point 58 corresponds to the point 40 of the punch. The locating pin 52 is positioned in a die block indicated at 60. The blank having a portion of thread formed from one face is located on the pin 52 with the portion 53 fitting into the impression 62 formed by the punch with the shoulder 45 acting to locate the blank. The punch 64 is the same as the punch 20 previously described and is positioned in a die block indicated at 66 with the axis of the punch in alignment with the axis of the pin. The punch 64 is positioned radially in relation to the pin 52 so that point 68 corresponding to point 40 of the punch is in line with point 58 of the pin. The punch is forced into the metal until the point 70 that corresponds to point 44 of the punch 20 is into the aperture a distance of one half of the thickness of the blank Where the portion of the thread being formed is in alignment with the portion of the thread formed from the opposite face. The punch is withdrawn and the blank removed from the pin.

While the foregoing operation has been described as designed to form a portion of a thread from one side of the blank at a time, it will of course be understood that the thread can be formed from both sides at the same time by providing a punch at each side of the die set and locating the blank by means other than the aperture.

The apparatus for carrying out the invention has been disclosed in the foregoing manner for purposes of clarification. It will beappreciated that othertypes of pressing apparatus can be used to carry out the pressing operation. If desired, a progressive type die whereby a strip of metal stock can be fed into one side and the operation performed continuously in succeeding stations of the die,

It will also be appreciated that a device can be used. having other shapes and forms can be produced in suitable dies in the pressing operation. For instance the blank can be made round or irregular in shape or if desired projections can be pressed from one face of the blank and the device used as a welding type nut.

Such modifications of my invention may be employed as lie withinthe scopeof the appendedclaims without departing from the spirit and intention of the invention.

What I claim as my invention is:

1. The method of forming a screw thread in a metal blank with a punch having an end portion provided with a surface shaped to correspond to one side of the thread to be formed, comprising providing a metal blank, having an aperture therein of a diameter approximately equal to the major diameter of the thread to be formed, applying pressure with the punch against the metal adjacent one end of the aperture beginning at the point of initial contact of the punch with the metal and continuing progressively around the aperture with the outer periphery of contact of the punch with the metal increasing in radius in respect to the axis of the aperture as the punch is forced inwardly thus forcing a fiow of metal axially and radially inwardly of the aperture against the thread shaping surface of the punch.

2. The method of forming a screw thread in a metal blank with a punch having an end portion provided with a surface shaped to correspond to one side of the thread to be formed, comprising providing a metal blank with an aperture therein having a diameter approximately equal to the major diameter of the thread to be formed, applying pressure with the punch against the metal adjacent one end of the aperture beginning at the point of initial contact of the punch with the metal of the blank and continuing progressively around the aperture with the outer periphery 'of contact of the punch with the blank increasing in radius in respect to the axis of the aperture as the punch is forced inwardly, forcing a flow of metal axially and radially inwardly of the aperture against the thread shaping surface at the end of the punch, thereafter applying pressure with the punch against the metal adjacent the opposite end of the aperture beginning at the initial contact of the punch with the metal at a point properly phased circumferentially with respect to the thread formed by the preceding step, and continuing progressively around the aperture with the outer periphery of contact of the punch with the blank increasing in radius with respect to the axis of the aperture as the punch is forced inwardly, thus forcing a flow of metal axially and radially inwardly of the aperture against the thread shaping surface at the end of the punch.

3. The method of claim 2 in which the thread formed from one side of the aperture joins with the thread formed from the opposite end of the aperture to form a substantially continuous thread.

4. The method of forming a screw thread in a metal blank with a punch having an end portion provided with a thread shaping surface formed to correspond to one side of the thread to be formed in the blank, comprising providing a blank having an aperture whose diameter is approximately equal to the major diameter of the thread to be formed,. applying pressure with the punch against the metal adjacent an end of the aperture beginning at the point of initial contact of the punch with the blank and continuing progressively around the aperture with the outer periphery of contact of the punch with the blank increasing in radius in respect to the axis of the aperture as the punch is forced inwardly of the aperture, thus forcing a fiow of metal axially and radially inwardly of the aperture against the thread shaping surface at the end of the punch and against a thread shaping surface at the end of a locating pin received in the I aperture.

5. A punch for forming a thread within a cylindrical opening in a blank, the opening having a diameter approximately equal to the root diameter of the thread to be formed, said punch having a helically disposed thread shaping surface of less than 360 degrees angular extent and conforming to a desired thread form, a metal deforming surface located to extend generally radially outwardly from the outer edge of said thread shaping surface, and a generally cylindrical surface intersecting said metal deforming surface at its radially outer edge and forming a curved shearing edge therewith, the radial dimension of said metal deforming surface being progressively larger from the end thereof positioned to make initial contact with said blank to the other end to provide uniform thread fullness in the blank.

6. Apparatus for forming a thread within a cylindrical opening in a blank, the opening having a diameter approximately equal to the root diameter of the thread to be formed, comprising a support having a locating pin edge and forming a curved shearing edge therewith, the radial dimension of said metal deforming surface being progressively larger from the end thereof positioned to make initial contact with said blank to the other end to provide uniform thread fullness in the blank, the thread shaping surfaces of said die and pin being movable to shape the metal sheared from said blank and displaced by the metal deforming surface into desired form therebetween.

References Cited in the file of this patent UNITED STATES PATENTS 1,247,854 MacLean Nov 27, 1917 6 Tinnerman Nov. 28, 1939 Bradford Sept. 30, 1941 Young Apr. 7, 1942 Squire July 7, 1942 Hilton Apr. 30, 1946 West Sept. 23, 1947 Mageoch May 18, 1948 FOREIGN PATENTS Austria Dec. 1, 1913 Great Britain Aug. 31, 1943 

